1. Field of the Invention
The present invention relates to interferometric observations; and more particularly, to a method and system for measuring the position of lightning strokes in real time.
2. Discussion of Related Art
In the vicinity of airports where planes are in the process of gaining altitude, circling the terrain awaiting landing and decreasing altitude in preparation for a landing, it is desirable that turbulence can be avoided in order to insure the comfort of the passengers and prevent needless mishaps.
Turbulence lightning strokes are the result of thunderstorms. Thus, if an airport control tower knows the location of lighting strokes, and is able to advise the incoming or outgoing planes of alternate paths, exposure to turbulence in most instances may be minimized or avoided by changing direction or altitude.
At close distances lightning strokes from clouds t ground are visible; and even some cloud to cloud lightning strokes may be observed. However, for the most part lightning strokes, and thus areas of turbulence, which occur within clouds or from cloud to cloud or even cloud to ground are not visible from either the ground, or the air at meaningful locations and distance.
Thus, it is desirable to be able to measure the position of lightning strokes in real time so that the control tower can direct planes to areas of less turbulence, and/or determine the rate and direction of storm movement.
Typically, systems for measuring the location of lightning strokes measure pulse arrival time at two different receivers. Such systems, which must use signals with some form of identifiable time structure work well for single pulses, or for pulses which are widely separated in time. However, if the pulses are closely spaced in time, and originate from different locations, as frequently is the case with lightning, it is possible for the order of the pulses to be confused at the different stations.
Another approach to the ambiguity of resolution of the time delay of arrival (TDOA) measurements is to use secondary characteristics of the pulse, such as shape and duration. This approach also runs into problems if the pulses overlap significantly. It is suitable only for post-real-time analysis because the intervention of a skilled experimenter is required in order to identify patterns in the data.